/Engine/Source/Runtime/GeometryCore/Public/MeshRegionBoundaryLoops.h
Ok, bdry_edges[0...bdry_edges_count] contains the boundary edges coming out of bowtie_v. We want to pick the best one to continue the loop that came : to bowtie_v on incoming_e. If the loops are all sane, then we will get the smallest loops by "turning left" at bowtie_v.
int FindLeftTurnEdge ( int incoming_e, int bowtie_v, [TArray](API\Runtime\Core\Containers\TArray)< int > & bdry_edges, int bdry_edges_count, const [FIndexFlagSet](API\Runtime\GeometryCore\Util\FIndexFlagSet) & used_edges )